The present invention relates to a foundation formed from one or more layers of tires. When the term xe2x80x9cfoundationxe2x80x9d is used herein, it includes any weight bearing surface such as a roadway, building foundation, railway track base, etc and any causeway including drainage floors, flow channels, drainage pit base, water sump, trickle filter base, bank way (including wave mat banks in water break walls) etc. The term xe2x80x9cfoundationxe2x80x9d is not intended to include retaining walls or the like (which are covered in the applicant""s co-pending application WO 98/49400), although various retaining walls are disclosed herein.
The use of tires (especially used tires) in retaining walls and retaining slopes is known. AU 10006/95 suggests a use for old tires by providing a trench formed to accommodate the tires in a side by side position to form a drain, tunnel, duct, ventilation shaft or the like.
FR 2643400 discloses a surface stabiliser formed from tires set in straight lines and forming squares, with one tire at each corner of a square. Alternatively, the tires can be provided in staggered rows with adjacent tires forming triangles. The tires are bound together using natural synthetic fibres and can be filled with pieces of rock and covered, after laying, with rock or stones and a layer of soil to receive plants etc. However, FR 2643400 only discloses a single row of tires, and does not disclose any structures which would be suitable for use in high load or highly erosive environments.
Similarly, RU 2060610 discloses a terracing arrangement employing used tires in a staggered arrangement (FIG. 2 therein). Again, the arrangement disclosed in this document is not suitable for use in high load or highly erosive environments, but is concerned with providing a simple mat-type structure to prevent land erosion from rain.
NL 7706564 discloses a mattress for reinforcing an underwater structure. A plastic fabric has tires secured thereto and a weighting material (a coarse rock) is positioned in those tires. In such an arrangement, the coarse material is highly susceptible to ingress of fines material and thus breakdown. In addition, the tires are simply provided to carry the weighting material so as to hold the plastics underlay in position. The arrangement is not concerned with load bearing applications.
SU 1312130 discloses a slope covering formed from old car tires. The structure includes a protective earth layer reinforced with used tires over which a stone material reinforcement layer, also reinforced with used tires, is laid. Junction elements are provided between the tire layers to join the two together. In addition, a polymer screen to prevent the earth layer from being leached from the structure is provided, but again there is nothing to suggest any substantial anti-erosive performance or load bearing capacity.
RU 2043455 discloses a road bed construction method which involves forming a mat of tires which are secured in the lengthwise direction. The tires are connected at their treads, are then covered with earth, peat or sand and are then covered with a geotextile layer. However, the construction does not prevent the ingress of fine materials into the mat, and thus would deteriorate over time.
U.S. Pat. No. 5,823,711 discloses a water drainage system formed from scrap tires. The system is designed to collect water therein for pumpout at a later stage. In this regard, a water impervious layer is positioned under the tires to capture/trap water within the tires.
In a first aspect the present invention provides a foundation comprising one or more layers of tires including a lowermost layer being located adjacent to the ground on a porous geofabric material, with tires in the lowermost layer having an upper sidewall removed therefrom and being provided therewithin with a fill material having a preselected grade, wherein the lowermost layer is enclosed within the geofabric material, and further fill material having a preselected grade and/or one or more further layers of tires overlay the enclosed lowermost layer to define the foundation.
By removing upper sidewalls from tires within the lowermost layer, fill material can be compacted therewithin, and then by enclosing the lowermost layer within a porous geofabric material an anchor for the foundation can be provided which is free-draining.
Preferably, the geofabric material is adapted for allowing the passage of water through the lowermost layer whilst preventing the ingress of matter of a grade finer than the fill material into the lowermost layer. This prevents deterioration of the fill material within the layer by the ingress of finer surrounding material.
The present invention also provides a method of construction on ground of a foundation as defined in the first aspect including the steps of:
positioning on the ground the geofabric material;
locating the lowermost layer of tires on the geofabric material;
filling tires in the lowermost layer with the fill material; and
folding the geofabric material to enclose the lowermost layer within the geofabric material.
Preferably the method includes a further step of overlaying the enclosed lowermost layer with the further fill material and/or the one or more further layers of tires.
Foundations constructed in accordance with the present invention can be suitably employed on: roads; ground or sub base such as sand and wetlands; drainage ways, courses and channels; railway track bases; mining tunnels; ramps and slopes adjacent to lakes, rivers, creeks, oceans; wave dissipation and breakwater walls; waste cell pits; stockpile bases, pavements; silt traps etc. All such environments are susceptible to erosion and deterioration through water saturation, and previous barriers employed.
In the foundation and the method of constructing the same, it is preferred that the tires within each of the layers are laid generally horizontally and are located adjacent to one another in a fixed array, each of the layers in conjunction with the fill material forming a tire mattress. Such a xe2x80x9cmattressxe2x80x9d construction provides a very stable foundation base and tends to resist erosion and provide high load bearing capacity.
Preferably each tire in each layer has a sidewall removed therefrom so that the tires can be oriented to be generally upwardly open in use to receive the fill material therein. When each tire is open (having its uppermost sidewall removed therefrom) fill can be readily compacted in each tire and an extremely stable and strong foundation can be constructed.
Typically the fill material is a rock aggregate or cobble of a relatively coarse grade. Such fill can be susceptible to dislocation and movement in use if finer material (such as sand) penetrates into the foundation structure. This is because the fine material xe2x80x9clubricatesxe2x80x9d the rock and reduces the interlock between aggregate pieces.
The number of layers employed in the foundation typically depends on the anticipated loadings and required stability of the foundation (eg when it is employed as an underlying road, ground or sub-base).
Typically, the lowermost layer is laid on the ground with minimal earthworks or sub-grade excavation being required. Advantageously, the foundation requires relatively low sub-grade stability and is thus suitable in marsh or swamp land and other wet areas. The layers of tires or tire mattresses can also be offset with respect to adjacent layers to provide distribution of the load between adjacent tires whilst reducing the stability (bearing pressure capacity) requirements of the underlying ground or sub-base (eg. one tire in one layer can overlay up to four tires in an underlying adjacent layer).
Preferably, the fill material is a rock aggregate or cobble of a relatively coarse grade. In one example, the rock aggregate fill is of a nominal 75 mm diameter. The relatively coarse fill material provides a porous layer having high drainage capacity. The relatively coarse fill material also combines with the tires to minimise degeneration of the roadway or the drainage floor.
The performance of the coarse grade fill can deteriorate if fine material ingresses into the foundation, thus providing another reason for the use of porous geofabric material. Dislocation and movement of the rock aggregate can lead to potholes in gravel roadways etc. Thus, the lowermost layer is wrapped in the geofabric material. In one example, the geofabric material is a geofabric cloth which also serves as a fire retardant.
When the foundation is used in a roadway or similar it can further comprise an edge support structure being configured to locate on opposing sides of at least an uppermost layer of the layers of tires, the support structure acting so as to inhibit movement of the tires and degeneration of the foundation. In one embodiment the edge support structure includes a row of support tires being located alongside and coupled via a link structure to at least one side of eg. the uppermost layer of tires.
Typically, the link structure includes a series of lateral tie elements each linking one of the support tires to an adjacent tire of the uppermost layer, and a longitudinal link element interconnecting the tie elements. In one example, the lateral tie elements and longitudinal link elements are constructed of tire tread connected end-to-end or alternatively of conveyor belt material. However, other alternatives are also possible (detailed below).
The foundation can also comprise a series of drainage tires located adjacent to one another within a trench excavated underneath the lowermost layer of tires, and a drainage fill material can be provided within or between the drainage tires. One or more drainage channels can extend from the trench so as to drain water away from the roadway or the drainage floor.
Typically the tires employed as the basic constructional element have intact tread portions (i.e. a whole tire is typically used, except that it typically has an upper side wall removed therefrom. However, in some applications such as in drainage channels, silt traps etc, part tires may be employed. For example, half a tire having an upper side wall removed therefrom can be employed, and various other tire segments can be employed.
In addition, tires within the foundation can be further strengthened by arranging tire portions therewithin as additional reinforcement. For example, in addition to fill material, a tire with an upper sidewall removed therefrom can have one or more coiled tire treads arranged therewithin, or a stack of tire sidewalls arranged therewithin, or combinations thereof etc.
Silt trap foundations in accordance with the present invention can be formed by arranging lengthwise a single row of tires, and by wrapping the row with tire tread or conveyor belt to form an integrated and portable unit. Preferably such units have three tires arranged end-to-end, each tire having an upper sidewall removed therefrom, with tire tread or conveyor belt extending around and joined to the tires.